type Vb, S-1 1996 BOCA to 2006 IBC

[rktect 1]

I have a building that was built in 2004 under the 1996 BOCA. It was designed as a type VB as an S-1 with sprinkler increase and being used as B doctors offices.

So under BOCA 96 it was a single story (story increase to 2 for sprinklers) of 4,200 sq. ft. with 200% increase as S-1 for a total of 12,600 sq. ft. And built at around 12,400 sq. ft. single story. That was their max at the time.

Today, if someone was to design this same building under the 2006 IBC an S-1 is allowed 9,000 sq. ft. with the sprinkler increase of 200% for a max. area of 27,000 and 2 stories for the increase.

Does this sound correct? Could someone now add 14,600 sq. ft. more to this same building? Could they also redesign it for a 2nd floor or 3rd floor under B use which would give the same square foot of 27,000?

Nobody is suggesting this but a plan came in for remodel on this site and I got to wondering. Especially when they didn't do their homework and wanted to call it a IIIB, B use and all of a sudden this building would be allowed to be 95,000 sq. ft and 5 stories tall. Again, nobody suggesting to add any floor or sq. ft.

 

[TJacobs]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

I have a building that was built in 2004 under the 1996 BOCA. It was designed as a type VB as an S-1 with sprinkler increase and being used as B doctors offices.So under BOCA 96 it was a single story (story increase to 2 for sprinklers) of 4,200 sq. ft. with 200% increase as S-1 for a total of 12,600 sq. ft. And built at around 12,400 sq. ft. single story. That was their max at the time.

Using 1996 BOCA, if you called it a B use instead of the S-1, you could have built 2 stories 7,200 sq. ft. tabular, a sprinkler increase of 14,400 sq. ft. for a total of 21,600 sq. ft.

Today, if someone was to design this same building under the 2006 IBC an S-1 is allowed 9,000 sq. ft. with the sprinkler increase of 200% for a max. area of 27,000 and 2 stories for the increase.

And a B is allowed 2 stories tabular instead of 1, so you would be able to get 3 stories with sprinklers.

Does this sound correct? Could someone now add 14,600 sq. ft. more to this same building? Could they also redesign it for a 2nd floor or 3rd floor under B use which would give the same square foot of 27,000?Nobody is suggesting this but a plan came in for remodel on this site and I got to wondering. Especially when they didn't do their homework and wanted to call it a IIIB, B use and all of a sudden this building would be allowed to be 95,000 sq. ft and 5 stories tall. Again, nobody suggesting to add any floor or sq. ft.

I would say yes they could, but I would be making them declare the B Group for the building if they added a floor, and maybe bring the entire building up to today's code. Heck, they can have an unlimited area, 2-story, any type, B Group building if they have the open space (507.4).

 

[pyrguy]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

You have to be careful of how you apply the sprinkler increase. Depending of the code edition you may only be able to have area or story not both.

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Nobody is suggesting this but a plan came in for remodel on this site and I got to wondering. Especially when they didn't do their homework and wanted to call it a IIIB, B use and all of a sudden this building would be allowed to be 95,000 sq. ft and 5 stories tall. Again, nobody suggesting to add any floor or sq. ft.

Not quite 95, 000 sf. Assuming IIIB, B group Table 503.1 allows 19,000 sf, 4 stories, 55' height. Assuming full open perimeter adds 1.75 x 19000 = 33,250 sf. Sprinkler increases adds 2 x 33,250 = 66,500 sf, one story and 20 feet. So it now totals 99,750 sf, 5 stories, and 75' high. Now apply the area adjustment in 506.4, since this is 3 stories or more, the adjusted maximum area per floor is 99,250 x 3 = 299250 divided by 5 stories = 59,850 sf per floor maximum.

That doesn't make me feel more secure, but it is better than 95,000 or 99,250 sf per floor.

Math and interpretation corrections welcomed.

Dan K

Architect, Building Official, Plans Examiner

 

[jar546]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Welcome Dan K. Glad to have you here and participating.

 

[peach]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

when you start talking about area and height increases.. you can get a very big building BEFORE they sprinkle the building... particularly if it falls into the category of not having to be sprinklered in the first place..

 

[kilitact]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

plans approver wrote;

Not quite 95, 000 sf. Assuming IIIB, B group Table 503.1 allows 19,000 sf, 4 stories, 55' height. Assuming full open perimeter adds 1.75 x 19000 = 33,250 sf. Sprinkler increases adds 2 x 33,250 = 66,500 sf, one story and 20 feet. So it now totals 99,750 sf, 5 stories, and 75' high. Now apply the area adjustment in 506.4, since this is 3 stories or more, the adjusted maximum area per floor is 99,250 x 3 = 299250 divided by 5 stories = 59,850 sf per floor maximum.That doesn't make me feel more secure, but it is better than 95,000 or 99,250 sf per floor.

Math and interpretation corrections welcomed.

The maximum area of the building would be a total of 427,500 sq ft or 85,500 sq ft per floor, if using Section 506.4 exception 2 which allows, if the building is equipped throughout with an automatic sprinkler in accordance with Section 903.3.1.2, that the maximum area shall be determined by multiplying the allowable area per story (Aa) as determined in Section 506.1, by the number of stories above grade plane.

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

The maximum area of the building would be a total of 427,500 sq ft or 85,500 sq ft per floor, if using Section 506.4 exception 2 which allows, if the building is equipped throughout with an automatic sprinkler in accordance with Section 903.3.1.2, that the maximum area shall be determined by multiplying the allowable area per story (Aa) as determined in Section 506.1, by the number of stories above grade plane.

Exception 2 applies to Group R buildings as the sprinkler section cited is 903.3.1.2 for NFPA 13R systems rather than 903.3.1.1 for NFPA 13 systems as required by 506.3.

Dan K

Architect, Building Official, Plans Examiner

 

[TJacobs]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Nobody is suggesting this but a plan came in for remodel on this site and I got to wondering. Especially when they didn't do their homework and wanted to call it a IIIB, B use and all of a sudden this building would be allowed to be 95,000 sq. ft and 5 stories tall. Again, nobody suggesting to add any floor or sq. ft.

Not quite 95, 000 sf. Assuming IIIB, B group Table 503.1 allows 19,000 sf, 4 stories, 55' height. Assuming full open perimeter adds 1.75 x 19000 = 33,250 sf. Sprinkler increases adds 2 x 33,250 = 66,500 sf, one story and 20 feet. So it now totals 99,750 sf, 5 stories, and 75' high. Now apply the area adjustment in 506.4, since this is 3 stories or more, the adjusted maximum area per floor is 99,250 x 3 = 299250 divided by 5 stories = 59,850 sf per floor maximum.

That doesn't make me feel more secure, but it is better than 95,000 or 99,250 sf per floor.

Math and interpretation corrections welcomed.

Dan K

Architect, Building Official, Plans Examiner

I forgot to add that a Type IIIB requires 2-hour exterior structural protection, so unless they can prove that they stay at VB at much less sq. ft.

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

I forgot to add that a Type IIIB requires 2-hour exterior structural protection, so unless they can prove that they stay at VB at much less sq. ft.

Not really. Two hours are required for exterior bearing walls and exterior non-bearing walls may require a rating depending on fire separation distance (Table 602). However, all IIIB exterior walls must be noncombustible (602.3). It is possible to have a masonry, concrete, or curtain wall non-bearing exterior wall with a wood structure just inside. It just depends on the design submitted.

Dan K

Architect, Building Official, Plans Examiner

 

[kilitact]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Exception 2 applies to Group R buildings as the sprinkler section cited is 903.3.1.2 for NFPA 13R systems rather than 903.3.1.1 for NFPA 13 systems as required by 506.3.

I would agree if we're considering a four story, this is a five story which would need a NFPA 13 system, still in accordance with sec. 903.3.1.1

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

I would agree if we're considering a four story, this is a five story which would need a NFPA 13 system, still in accordance with sec. 903.3.1.1

I must not be making myself clear. The original hypothesis was the maximum size of a group B building of IIIB construction, fully sprinklered. I calc'd out 59,850 sf.

The maximum area of the building would be a total of 427,500 sq ft or 85,500 sq ft per floor, if using Section 506.4 exception 2 which allows, if the building is equipped throughout with an automatic sprinkler in accordance with Section 903.3.1.2, that the maximum area shall be determined by multiplying the allowable area per story (Aa) as determined in Section 506.1, by the number of stories above grade plane.

I replied that this exception did not apply to the hypothetical case and only applied to R buildings, because you can't put a 13R (903.3.1.2) system in a B building, and therefore, can not take the 200% area increase. The maximum area per floor for any building, except R see below, 3 stories or more in height is Aa x 3 divided by the number of floors. All buildings w/ a floor occupant load greater than 30 and the floor is => 55' high is required to have a 13 system w/ 3 exceptions for height not area.

There are no area increases for 13R systems. There is a height increase for 13R systems of one story and 20 feet up to a maximum of 4 stories and 60 feet. R use beyond those limits require an full 13 system.

Dan K

Architect, Building Official, Plans Examiner

 

[kilitact]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

plans approver wrote:

There are no area increases for 13R systems. There is a height increase for 13R systems of one story and 20 feet up to a maximum of 4 stories and 60 feet. R use beyond those limits requires a full 13 system

My point was that if you exceed four stories, you’re required to install a 13 system. The exception states, buildings, this appears to not be specific to any occupancy.

My calculations for a five story B occupancy would be 64,125 sq ft per floor, I would use the exception for sprinklers and call this a III-A

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

My point was that if you exceed four stories, you’re required to install a 13 system.

Where is that in the code for other than R and I-1 buildings w/ NFPA 13R systems?

The exception states, buildings, this appears to not be specific to any occupancy.

You're right, but... This is a section that needs to be fixed (and they didn't in the 2009 edition) that says certain occupancy groups without specifically saying which ones. As we know, 13 systems can be used in all buildings, 13R systems can only be used in residential type occupancies such as any of the R's and I-1, and 13D in 1 & 2 family dwellings and I-1.

Exception 2 of 506.4 specifically cites 903.3.1.2 which says: "NFPA 13R sprinkler systems. Where allowed in buildings of Group R, up to and including four stories in height, automatic sprinkler systems shall be installed throughout in accordance with NFPA 13R." The only occupancy, other than R, mentioned in the code that can use a 13R system is I-1 in the exception to 903.2.5.

The purpose of the exception is to not penalize 4 story, sprinklered R (and I-1) buildings with the 3 story limit.

My calculations for a five story B occupancy would be 64,125 sq ft per floor, I would use the exception for sprinklers and call this a III-A

Ok, now you are within 5000 sf of me. How did you get there? What exception for sprinklers? If you use the 200% area increase, you can not use the 1 hour construction rating deduction (Table 601, footnote e and 506.3, Exception 3).

Enjoying the discussion...

Dan K

Architect, Building Official, Plans Examiner

 

[kilitact]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

that should work

 

[EPrice]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Not quite 95, 000 sf. Assuming IIIB, B group Table 503.1 allows 19,000 sf, 4 stories, 55' height. Assuming full open perimeter adds 1.75 x 19000 = 33,250 sf. Sprinkler increases adds 2 x 33,250 = 66,500 sf, one story and 20 feet. So it now totals 99,750 sf, 5 stories, and 75' high. Now apply the area adjustment in 506.4, since this is 3 stories or more, the adjusted maximum area per floor is 99,250 x 3 = 299250 divided by 5 stories = 59,850 sf per floor maximum.That doesn't make me feel more secure, but it is better than 95,000 or 99,250 sf per floor.

Math and interpretation corrections welcomed.

Dan K

Architect, Building Official, Plans Examiner

Aa = {At + [At x If] + [At x Is]} (equation 5-1)

= {19,000 + [19,000 x .75] + [19,000 x 2]}

= 19,000 + 14,250 + 38,000

= 71,250 sq. ft. per floor

71,250 x 3 = 213,750 sq. ft. total allowed for building.

213,750 / 5 = 42,750 sq. ft. per floor if all 5 floors are to be equal in area

Edit to add: A building with the following floor areas would also be code compliant:

71,250 sq. ft. 1st floor

71,250 sq. ft. 2nd floor

23,750 sq. ft. 3rd floor

23,750 sq. ft. 4th floor

23,750 sq. ft. 5th floor

 

[Plans Approver]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

Aa = {At + [At x If] + [At x Is]} (equation 5-1)

= {19,000 + [19,000 x .75] + [19,000 x 2]}

= 19,000 + 14,250 + 38,000

= 71,250 sq. ft. per floor

71,250 x 3 = 213,750 sq. ft. total allowed for building.

213,750 / 5 = 42,750 sq. ft. per floor if all 5 floors are to be equal in area

Edit to add: A building with the following floor areas would also be code compliant:

71,250 sq. ft. 1st floor

71,250 sq. ft. 2nd floor

23,750 sq. ft. 3rd floor

23,750 sq. ft. 4th floor

23,750 sq. ft. 5th floor

Bingo! Thanks for the correction.

 

[kilitact]

Re: type Vb, S-1 1996 BOCA to 2006 IBC

glad we got sombody that got it right.